Carb Rebuild
in 912 / 914 Technical Questions
11 years ago
912ULS, 630 hours, rebuilt the carbs this weekend. Used the LEAF deluxe rebuild kit and replaced the rubber flange assembly's (carb sockets) at the same time. I used the ROTAX carb disassembly, cleaning and reassembly videos, did one carb at a time and did a carb balance (from idle to 3500 rpm, idle set at 1800 rpm) following the reassembly.
Engine runs great, has never been smoother.
One problem, when cold (this is Florida, 65 to 75 degree F.)and using the choke fully applied and the throttle at idle the engine starts but seems to be running very rough just above starting speed, maybe 500-600 rpms. Quickly applying more throttle doesn't seem to make the engine rpm's want to increase, it just sits at that rpm and shakes and stumbles. Starts with the choke not activated and with the throttle just above idle are fine with a smooth start and about 2200-2500 rpm. I bought this plane at 430 hours and have always used the choke for the first start of the day and it is usually rough at first but smooth's out once I advance the throttle to 2500 rpm or so.
I verified I installed the choke disc correctly with the dot towards the choke air inlet, no mix-up of parts since I did one carb at a time, the chokes track together and hit both the off and full on stops together. I also did a carburetor operational check shown on this website called a mixture check; it states, "run the engine at 2200 rpm and slowly open the choke. You should get about a 400-600 rpm rise. As the choke is fully opened you should start to lose rpm". My engine does exactly as this states, so I assume: 1) the mixture is right and 2) the chokes are acting as they should to en-richen the mixture and are balanced because the engine remains running smoothly up to 2800 rpm.
Anyone have any ideas on what I did wrong or proper starting techniques at this temperature.
Thanks,
Ron Greene
Engine runs great, has never been smoother.
One problem, when cold (this is Florida, 65 to 75 degree F.)and using the choke fully applied and the throttle at idle the engine starts but seems to be running very rough just above starting speed, maybe 500-600 rpms. Quickly applying more throttle doesn't seem to make the engine rpm's want to increase, it just sits at that rpm and shakes and stumbles. Starts with the choke not activated and with the throttle just above idle are fine with a smooth start and about 2200-2500 rpm. I bought this plane at 430 hours and have always used the choke for the first start of the day and it is usually rough at first but smooth's out once I advance the throttle to 2500 rpm or so.
I verified I installed the choke disc correctly with the dot towards the choke air inlet, no mix-up of parts since I did one carb at a time, the chokes track together and hit both the off and full on stops together. I also did a carburetor operational check shown on this website called a mixture check; it states, "run the engine at 2200 rpm and slowly open the choke. You should get about a 400-600 rpm rise. As the choke is fully opened you should start to lose rpm". My engine does exactly as this states, so I assume: 1) the mixture is right and 2) the chokes are acting as they should to en-richen the mixture and are balanced because the engine remains running smoothly up to 2800 rpm.
Anyone have any ideas on what I did wrong or proper starting techniques at this temperature.
Thanks,
Ron Greene
